The Kindle Fire from Amazon has stolen a march in the tablet world, with some estimating that it now makes up more than half of all Android tablets in use in the U.S. today. But the latest monthly figures from mobile ad network JumpTap today paint a different picture in terms of usage.

JumpTap noted that in the months after its launch, Amazon’s device rapidly picked up market share, reaching 33 percent of all traffic on its network in January 2012. But since then, the figure has gradually been in decline and is now at 22 percent. Meanwhile, Apple’s iPad — which had lost share to the Kindle Fire — is now back to 65 percent, or where it was before Amazon launched its tablet.

JumpTap, which bases its numbers on ad impressions on its network, noted that the Fire tablet came its closest to the iPad’s traffic share in January, when the iPad’s share of traffic had declind down to 48 percent.

Meanwhile, the rest of the tablet market seems to be stalling out: collectively, the others currently account for 14 percent of all traffic on JumpTap’s network, the same proportion they had for the past three months.

In fact, the rest of the tablet market, excepting the iPad, seems to have been hit the worst by the rise of the Kindle Fire: together, they made up 31 percent of all traffic on JumpTap’s network back in November 2011 — in other words, their share has more than halved.

So why the decline for the Kindle Fire, and the growth for the iPad? JumpTap attributes it to strong sales of the newest iPad. But it could also be that while the Kindle saw a big boost in purchases after its launch and during the holiday period, it could be that some of the novelty of the product has worn off and people are now using it less.

However, important to note that JumpTap says that even as the Kindle’s share of traffic has declined, in real terms usage has actually increased three-fold over Q4 2011 as a result of the overall growth in tablet usage. It doesn’t give comparative traffic numbers for other devices.